The present invention relates generally to conferencing systems, and more specifically to techniques for accessing enhanced conferencing capabilities.
Conferencing systems are known that employ the Session Initiation Protocol (SIP) to establish and manage multimedia sessions (also known as “conferences”) over computer networks. For example, a conference having zero or more conference participants may be established over a network by a conferencing application server, which communicates with each conference participant and at least one media server on the network using SIP call control signaling. In the event a prospective conference participant wishes to join the conference, the prospective participant sends a SIP request message to the conferencing application server. After receiving the SIP request message, the conferencing application server sends a corresponding SIP request message to at least one media server assigned to the conference.
In the event the conference Universal Resource Identifier (URI) exists on the media server, the media server sends a SIP 200 OK message to the conferencing application server to indicate that the prospective conference participant has been successfully joined to the conference. If the conference URI does not exist on the media server, then the desired conference is created before the media server sends the SIP 200 OK message. The conferencing application server then sends a corresponding SIP 200 OK message to the conference participant to indicate the participant's success in joining the conference. Next, the conference participant sends a SIP ACK message to the conferencing application server to acknowledge its receipt of the SIP 200 OK message, and the conferencing application server sends a corresponding SIP ACK message to the media server. Because the prospective conference participant has successfully joined the conference, a multimedia session is established during which multimedia data such as audio data is generated and conveyed between the media server and the conference participant.
In the event the conference participant wishes to be removed from the conference, the participant sends a SIP BYE request message to the conferencing application server, which in turn conveys the SIP BYE request to the media server. Next, the media server sends a SIP 200 OK message to the conferencing application server, which in turn conveys the SIP 200 OK message to the conference participant, thereby indicating that the participant has been successfully removed from the Conference. In this way, the conferencing application server can both create a multimedia conference and control prospective conference participants' access to the conference.
Although the above-described SIP call control signaling technique may be employed to establish and manage multimedia conferences, the technique has drawbacks in that it is generally not amenable to establishing and managing conferences that provide advanced conferencing features such as notification of conference events (e.g., the identification of conference participants whose voices are mixed into the audio output of the conference) or packet mixing for determining the scope of multimedia data delivery within a conference. The above-described technique also provides no mechanism for detecting and reporting media events such as DTMF/MF digits input by conference participants. Such events are commonly used to invoke advanced conferencing features. This is because conventional SIP call control signaling techniques employing SIP INVITE/BYE request messages typically do not provide interfaces that can easily access such advanced conferencing features.
It would therefore be desirable to have a conferencing system for establishing and managing multimedia conferences over computer networks. Such a conferencing system would employ enhanced call control signaling techniques to provide a conferencing application server/media server interface capable of accessing advanced conferencing features It would also be desirable to have a conferencing system that can access advanced conferencing features while following essentially the same call flow as conventional conferencing systems.